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  • 1
    Electronic Resource
    Electronic Resource
    Surface properties of solids using a semi-infinite approach and the tight-binding approximation (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7405-7411 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A semi-infinite approach (rather than a slab method or finite number of layers) is used to treat surface properties such as wave functions, energy levels, and Fermi surfaces of semi-infinite solids within the tight-binding (TB) approximation. Previous single-band results for the face-centered cubic lattice with a (111) surface and for the simple cubic lattice with a (001) surface are extended to semi-infinite layers, while the extension to calculations of other surfaces is straightforward. Treatment of more complicated systems is illustrated in the calculation of the graphite (0001) surface. Four interacting bands are considered in the determination of the wave functions, energies, and Fermi surface of the graphite (0001) surface. For the TB model used, the matrix elements in the secular determinants for the semi-infinite solid and for the infinite bulk solid obey the same expressions, and the wave functions are closely related. Accordingly, the results for the bulk system can then be directly applied to the semi-infinite one. The main purpose of the present paper is to provide wave functions and other properties used elsewhere to treat phenomena such as scanning tunneling microscopy and electron transfer rates at electrodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465096
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  • 2
    Electronic Resource
    Electronic Resource
    A theoretical model of scanning tunneling microscopy: Application to the graphite (0001) and Au(111) surfaces (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7565-7573 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An expression for the scanning tunneling microscopy (STM) current between the tip and sample is presented using first-order perturbation theory for a two-Hamiltonian formalism ("reactants'' and "products''). The calculated STM current depends on the square of the sample-tip matrix elements, averaged over a selection of random points in wave vector space. In the limit of low voltage and temperature, this averaging is over the Fermi surface of the sample. The model is applied to the graphite (0001) and Au(111) surfaces using a simple model (chain) of a tungsten tip and the tight-binding approximation. Comparisons with experiments and with the result for graphite obtained by Tersoff and Lang using a molybdenum tip are given. The theory is applied elsewhere to STM of adsorbates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464696
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  • 3
    Electronic Resource
    Electronic Resource
    Surface Phosphorylation by Ecto-Protein Kinase C in Brain Neurons: A Target for Alzheimer's β-Amyloid Peptides (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 65 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The powerful regulatory machinery of protein phosphorylation operates in the extracellular environment of the brain. Enzymatic activity with the catalytic specificity of protein kinase C (PKC) was detected on the surface of brain neurons, where it can serve as a direct target for neurotrophic and neurotoxic substances that control neuronal development and cause neurodegeneration. This activity fulfilled all the criteria required of an ectoprotein kinase (ecto-PK). Detailed analysis of surface protein phosphorylation in cultured brain neurons using specific exogenous substrates (casein, histones, and myelin basic protein), inhibitors (PKC-pseudosubstrate 19–36; K252b) and antibodies (anti-PKC catalytic region M.Ab.1.9, antibodies to the carboxy-terminus of eight PKC isozymes) revealed several types of ecto-PK activity, among them ecto-PKs with catalytic specificity of the PKC isozymes ζ and δ. The activity of the neuronal ecto-PKC is constitutive and not stimulated by phorbol esters. The phosphorylation of a 12K/13K surface protein duplex by ecto-PKC-δ was found to be developmentally regulated, with peak activity occurring during the onset of neuritogenesis. Alzheimer's amyloid peptides β1–40 and β25–35 applied at neurotrophic concentrations stimulated the phosphorylation of endogenous substrates of ecto-PKC activity in brain neurons but inhibited specifically this surface phosphorylation activity with the same dose-response relationships that cause neurodegeneration. As may be expected from a relevant pathophysiological activity, β-amyloid peptide 1–28 did not inhibit this surface phosphorylation. The discovery that ecto-PKC-mediated protein phosphorylation serves as a target for β-amyloid peptides at the very site they operate, i.e., at the neuronal cell surface, opens a new research direction in the investigation of molecular events that play a role in the etiology of developmental disabilities and neurodegenerative disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.65052022.x
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  • 4
    Electronic Resource
    Electronic Resource
    Cubic-phase GaN light-emitting diodes (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2498-2500 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The feasibility of growing device-quality cubic GaN/GaAs(001) films by metal organic chemical vapor deposition has been demonstrated. The optical quality of the GaN films was characterized by room-temperature photoluminescence measurements, which shows a full width at half maximum of 46 meV. The structural quality of the films was investigated by transmission electron microscopy. There are submicron-size grains free from threading dislocations and stacking faults. More importantly, a cubic-phase GaN blue light-emitting diode has been fabricated. The device process, which is very simple and compatible with current GaAs technology, indicates a promising future for the blue light-emitting diode. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123019
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  • 5
    Electronic Resource
    Electronic Resource
    Optimized growth conditions for the epitaxial nucleation of β-GaN on GaAs(001) by molecular beam epitaxy (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 473-475 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin (5–7 monolayers) nucleation layers of GaN are deposited on (2×4)-GaAs(001) by plasma-assisted molecular beam epitaxy. Reflection high-energy electron diffraction applied in situ reveals these layers to be epitaxial β-GaN. Transmission electron microscopy confirms this result and reveals in addition that the layers are highly connected and have an atomically abrupt interface to the GaAs substrate. The rms roughness of these layers, as measured by atomic force microscopy, is as low as 1.4 Å. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119583
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  • 6
    Electronic Resource
    Electronic Resource
    High p-type conductivity in cubic GaN/GaAs(113)A by using Be as the acceptor and O as the codopant (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2707-2709 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: P-type room-temperature conductivities as high as 50/Ω cm are achieved in cubic GaN layers by the concept of reactive codoping. We use Be as the acceptor species and O as the reactive donor to render isolated Coulomb scatterers into dipole scatterers. This concept allows us to achieve high hole mobilities and thus p-type conductivities. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117685
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  • 7
    Electronic Resource
    Electronic Resource
    Scanning tunneling microscopy theory for an adsorbate: Application to adenine adsorbed on a graphite surface (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 7814-7824 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An expression is obtained for the current in scanning tunneling microscopy (STM) for a single adsorbate molecule. For this purpose the "Newns–Anderson'' treatment (a "discrete state in a continuum'' treatment) is used to obtain wave functions and other properties of the adsorbate/substrate system. The current is expressed in terms of the adsorbate–tip matrix elements, and an effective local density of states of the adsorbate/substrate system, at the adsorbate. As an example, the treatment is applied to the STM image of adenine adsorbed on a graphite surface, and the results are compared with experiment. The dependence of the image on the position of adenine with respect to the underlying graphite is considered. A discussion is given of the type of experimental STM data needed for suitable comparison of theory and experiment. In an analysis of the calculations, the role of each atom, its neighbors, next nearest neighbors, etc., in an adsorbed molecule is considered. The need for using in the present calculation more orbitals than only the HOMO and the LUMO of the adsorbate is also noted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466824
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  • 8
    Electronic Resource
    Electronic Resource
    Intramolecular ring-opening reactions of 2-oxetanones leading to tetrahydrofuran ring formation: a Lewis-acid study (1990)
    s.l. : American Chemical Society
    The @journal of organic chemistry 55 (1990), S. 2991-2992 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00297a002
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  • 9
    Electronic Resource
    Electronic Resource
    Poly(alkyl thiophene-3-carboxylates). Synthesis and Characterization of Polythiophenes with a Carbonyl Group Directly Attached to the Ring (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 5706-5708 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00121a003
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  • 10
    Electronic Resource
    Electronic Resource
    A survey on dental care and oral implantology in Beijing, China (1997)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 8 (1997), S. 0 
    Details
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In this article,we present a survey on dental care and oral implantology in Beijing, China. The Chinese population comprises 1.2 billion or about 20% of the world's population. This survey shows: (i) there is a well-developed dental system in China, mostly operated by the Chinese government; (ii) in Beijing, there are 1328 dentists and oral surgeons and 515 special dental nurses working in dental departments of hospitals: (iii) about 2 million new patients visit the dentist every year; (iv) oral implantology is a new technology for the Chinese dentist and oral surgeon, as shown by the finding that in 1992, only 384 persons were treated with oral implants in a few hospitals in Beijing; however, most hospitals are interested in performing oral implantology in the near future; (v) imported implants are too expensive for Chinese patients, and therefore good qualified domestic implants and cheaper imported implants have a great market potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0501.1997.080301.x
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